Nav Menu meta failing to import

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1. The problem was ultimately with the WordPress Importer plugin. I could hack at it (and have suggested an improvement to the developers) but I am going to got around this by writing a custom Importer of my own. It isn’t the most convenient (to re-upload the .XML file) but in cases where users have complex menus it is better than losing the meta values.

   It needs more testing, but I should be adding it to my plugin in the next version.

   Custom Importer for Menu Item Meta

   The problem was ultimately with the WordPress Importer plugin. I could hack at it (and have suggested an improvement to the developers) but I am going to got around this by writing a custom Importer of my own. It isn’t the most convenient (to re-upload the .XML file) but in cases where users have complex menus it is better than losing the meta values.

   It needs more testing, but I should be adding it to my plugin in the next version.

   Custom Importer for Menu Item Meta

   <?php
   /**
    * Nav Menu Roles Importer - import menu item meta
    *
    */
   
   if ( ! defined( 'ABSPATH' ) ) exit; // Exit if accessed directly
   
   if ( class_exists( 'WP_Importer' ) ) {
       class Nav_Menu_Roles_Import extends WP_Importer {
   
       var $max_wxr_version = 1.2; // max. supported WXR version
   
       var $id; // WXR attachment ID
   
       // information to import from WXR file
       var $version;
       var $posts = array();
       var $base_url = '';
   
   
           /**
            * __construct function.
            *
            * @access public
            * @return void
            */
           public function __construct() {
               $this->import_page = 'nav_menu_roles';
           }
   
       /**
        * Registered callback function for the WordPress Importer
        *
        * Manages the three separate stages of the WXR import process
        */
       function dispatch() {
           $this->header();
   
           $step = empty( $_GET['step'] ) ? 0 : (int) $_GET['step'];
           switch ( $step ) {
               case 0:
                   $this->greet();
                   break;
               case 1:
                   check_admin_referer( 'import-upload' );
                   if ( $this->handle_upload() ) {
                       $file = get_attached_file( $this->id );
                       set_time_limit(0);
                       $this->import( $file );
                   }
                   break;
           }
   
           $this->footer();
       }
   
       /**
        * The main controller for the actual import stage.
        *
        * @param string $file Path to the WXR file for importing
        */
       function import( $file ) {
           add_filter( 'import_post_meta_key', array( $this, 'is_valid_meta_key' ) );
           add_filter( 'http_request_timeout', array( &$this, 'bump_request_timeout' ) );
   
           $this->import_start( $file );
   
           wp_suspend_cache_invalidation( true );
           $this->process_nav_menu_meta();
           wp_suspend_cache_invalidation( false );
   
           $this->import_end();
       }
   
       /**
        * Parses the WXR file and prepares us for the task of processing parsed data
        *
        * @param string $file Path to the WXR file for importing
        */
       function import_start( $file ) {
           if ( ! is_file($file) ) {
               echo '<p><strong>' . __( 'Sorry, there has been an error.', 'nav-menu-roles' ) . '</strong><br />';
               echo __( 'The file does not exist, please try again.', 'nav-menu-roles' ) . '</p>';
               $this->footer();
               die();
           }
   
           $import_data = $this->parse( $file );
   
           if ( is_wp_error( $import_data ) ) {
               echo '<p><strong>' . __( 'Sorry, there has been an error.', 'nav-menu-roles' ) . '</strong><br />';
               echo esc_html( $import_data->get_error_message() ) . '</p>';
               $this->footer();
               die();
           }
   
           $this->version = $import_data['version'];
           $this->posts = $import_data['posts'];
           $this->base_url = esc_url( $import_data['base_url'] );
   
           wp_defer_term_counting( true );
           wp_defer_comment_counting( true );
   
           do_action( 'import_start' );
       }
   
       /**
        * Performs post-import cleanup of files and the cache
        */
       function import_end() {
           wp_import_cleanup( $this->id );
   
           wp_cache_flush();
           foreach ( get_taxonomies() as $tax ) {
               delete_option( "{$tax}_children" );
               _get_term_hierarchy( $tax );
           }
   
           wp_defer_term_counting( false );
           wp_defer_comment_counting( false );
   
           echo '<p>' . __( 'All done.', 'nav-menu-roles' ) . ' <a href="' . admin_url() . '">' . __( 'Have fun!', 'nav-menu-roles' ) . '</a>' . '</p>';
   
           do_action( 'import_end' );
       }
   
       /**
        * Handles the WXR upload and initial parsing of the file to prepare for
        * displaying author import options
        *
        * @return bool False if error uploading or invalid file, true otherwise
        */
       function handle_upload() {
           $file = wp_import_handle_upload();
   
           if ( isset( $file['error'] ) ) {
               echo '<p><strong>' . __( 'Sorry, there has been an error.', 'nav-menu-roles' ) . '</strong><br />';
               echo esc_html( $file['error'] ) . '</p>';
               return false;
           } else if ( ! file_exists( $file['file'] ) ) {
               echo '<p><strong>' . __( 'Sorry, there has been an error.', 'nav-menu-roles' ) . '</strong><br />';
               printf( __( 'The export file could not be found at <code>%s</code>. It is likely that this was caused by a permissions problem.', 'nav-menu-roles' ), esc_html( $file['file'] ) );
               echo '</p>';
               return false;
           }
   
           $this->id = (int) $file['id'];
           $import_data = $this->parse( $file['file'] );
           if ( is_wp_error( $import_data ) ) {
               echo '<p><strong>' . __( 'Sorry, there has been an error.', 'nav-menu-roles' ) . '</strong><br />';
               echo esc_html( $import_data->get_error_message() ) . '</p>';
               return false;
           }
   
           $this->version = $import_data['version'];
           if ( $this->version > $this->max_wxr_version ) {
               echo '<div class="error"><p><strong>';
               printf( __( 'This WXR file (version %s) may not be supported by this version of the importer. Please consider updating.', 'nav-menu-roles' ), esc_html($import_data['version']) );
               echo '</strong></p></div>';
           }
   
           return true;
       }
   
   
   
       /**
        * Create new posts based on import information
        *
        * Posts marked as having a parent which doesn't exist will become top level items.
        * Doesn't create a new post if: the post type doesn't exist, the given post ID
        * is already noted as imported or a post with the same title and date already exists.
        * Note that new/updated terms, comments and meta are imported for the last of the above.
        */
       function process_nav_menu_meta() {
           foreach ( $this->posts as $post ) {
   
               // we only want to deal with the nav_menu_item posts
               if ( 'nav_menu_item' != $post['post_type'] || ! empty( $post['post_id'] ) )
                   continue;
   
               // ok we've got a nav_menu_item
               $post_id = (int) $post['post_id'];
   
               // add/update post meta
               if ( isset( $post['postmeta'] ) ) {
                   foreach ( $post['postmeta'] as $meta ) {
                       $key = apply_filters( 'import_post_meta_key', $meta['key'] );
                       $value = false;
   
   
                       if ( $key ) {
                           // export gets meta straight from the DB so could have a serialized string
                           if ( ! $value )
                               $value = maybe_unserialize( $meta['value'] );
   
                           update_post_meta( $post_id, $key, $value );
                           do_action( 'import_post_meta', $post_id, $key, $value );
   
                       }
                   }
               }
           }
   
           unset( $this->posts );
       }
   
   
   
   
       /**
        * Parse a WXR file
        *
        * @param string $file Path to WXR file for parsing
        * @return array Information gathered from the WXR file
        */
       function parse( $file ) {
           $parser = new WXR_Parser();
           return $parser->parse( $file );
       }
   
       // Display import page title
       function header() {
           echo '<div class="wrap">';
           screen_icon();
           echo '<h2>' . __( 'Import Nav Menu Roles', 'nav-menu-roles' ) . '</h2>';
   
           $updates = get_plugin_updates();
           $basename = plugin_basename(__FILE__);
           if ( isset( $updates[$basename] ) ) {
               $update = $updates[$basename];
               echo '<div class="error"><p><strong>';
               printf( __( 'A new version of this importer is available. Please update to version %s to ensure compatibility with newer export files.', 'nav-menu-roles' ), $update->update->new_version );
               echo '</strong></p></div>';
           }
       }
   
       // Close div.wrap
       function footer() {
           echo '</div>';
       }
   
       /**
        * Display introductory text and file upload form
        */
       function greet() {
           echo '<div class="narrow">';
           echo '<p>'.__( 'Re-Upload your normal WordPress eXtended RSS (WXR) file and we&#8217;ll import the Nav Menu Roles and any other missing post meta for the Nav Menu items.', 'nav-menu-roles' ).'</p>';
           echo '<p>'.__( 'Choose a WXR (.xml) file to upload, then click Upload file and import.', 'nav-menu-roles' ).'</p>';
           wp_import_upload_form( 'admin.php?import=nav_menu_roles&amp;step=1' );
           echo '</div>';
       }
   
       /**
        * Decide if the given meta key maps to information we will want to import
        *
        * @param string $key The meta key to check
        * @return string|bool The key if we do want to import, false if not
        */
       function is_valid_meta_key( $key ) {
           // skip attachment metadata since we'll regenerate it from scratch
           // skip _edit_lock as not relevant for import
           if ( in_array( $key, array( '_wp_attached_file', '_wp_attachment_metadata', '_edit_lock' ) ) )
               return false;
           return $key;
       }
   
   
       /**
        * Added to http_request_timeout filter to force timeout at 60 seconds during import
        * @return int 60
        */
       function bump_request_timeout() {
           return 60;
       }
   
       // return the difference in length between two strings
       function cmpr_strlen( $a, $b ) {
           return strlen($b) - strlen($a);
       }
   
   
       } // end class
   } // end if
   

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